What I need to do is this:
# My new CX3-40f which supports ALUA (preferred) as well as PNR
device {
vendor DGC
product *
product_blacklist LUNZ
alua_capable yes
[..ALUA optimised settings...]
}
# My old CX200, only supports PNR
device {
vendor DGC
product *
product_blacklist LUNZ
alua_capable no
[..PNR optimised settings...]
}
...but there's no such thing as the "alua_capable" setting or any other
setting that can be used to distinguish between the two CLARiiONs, as
far as I know, so I have to use both arrays in PNR mode even though the
newest one of them supports ALUA.

No need. I did some patch once ago which allowed you to set the hardware
handler in the multipaths section.
For exactly this scenario. Can you test if it works?
Cheers,
Hannes
--
Dr. Hannes Reinecke zSeries & Storage
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